AQA GCSE Biology
AQA GCSE Biology 4.4.2 Respiration Exam Questions
Free AQA GCSE Biology exam questions for 4.4.2 Respiration, with a mark scheme for every pack. Covers aerobic and anaerobic respiration in animals, plants and yeast, fermentation, the response to exercise, oxygen debt and metabolism.
4.4.2 Respiration exam questions
4 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA GCSE Biology 4.4.2 Respiration
Respiration completes AQA Bioenergetics on Paper 1. It explains how cells transfer energy from glucose by aerobic and anaerobic respiration, how the body responds to exercise, and how metabolism builds up and breaks down molecules. It links to mitochondria in 4.1.1, the heart and lungs in 4.2.2, photosynthesis in 4.4.1 and the carbon cycle in Ecology. Examiners often ask you to compare aerobic and anaerobic respiration, write word or symbol equations, interpret heart and breathing rate data, and (Higher tier only) explain oxygen debt and what happens to lactic acid.
What you need to know
- 4.4.2.1 Aerobic respiration Respiration is an exothermic reaction that happens continuously in living cells to supply energy. Aerobic respiration uses oxygen in the mitochondria: glucose + oxygen -> carbon dioxide + water; C6H12O6 + 6O2 -> 6CO2 + 6H2O.
- Anaerobic respiration In muscles during hard exercise: glucose -> lactic acid. In plant and yeast cells: glucose -> ethanol + carbon dioxide, which in yeast is called fermentation and is used to make bread and alcoholic drinks. Anaerobic respiration transfers much less energy because glucose is incompletely oxidised.
- Energy uses Organisms need energy for chemical reactions to build larger molecules, for movement, and for keeping warm.
- 4.4.2.2 Response to exercise During exercise heart rate, breathing rate and breath volume increase to supply more oxygenated blood to muscles. Prolonged activity causes muscle fatigue as muscles stop contracting efficiently.
- Oxygen debt (Higher tier only) Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from cells. Blood carries lactic acid to the liver, where it is converted back into glucose.
- 4.4.2.3 Metabolism Metabolism is the sum of all reactions in a cell or the body. It includes converting glucose to starch, glycogen and cellulose, forming lipids from glycerol and three fatty acids, using glucose and nitrate ions to form amino acids and proteins, respiration, and breaking down excess proteins to form urea for excretion.
Common mistakes in 4.4.2 Respiration
- Saying respiration produces energy. Energy cannot be made; respiration transfers energy from glucose.
- Confusing respiration with breathing. Respiration is a chemical reaction in cells; breathing is moving air in and out of the lungs.
- Saying anaerobic respiration in muscles produces carbon dioxide. In muscles the only product is lactic acid.
- Saying lactic acid is broken down in the muscles. It is carried by the blood to the liver and converted back to glucose (Higher tier only).
- Saying plants only respire at night. Plants respire all the time.
Try three 4.4.2 Respiration exam-style questions
1. Compare aerobic respiration and anaerobic respiration in muscle cells. (4 marks)
Show the mark scheme answer
Aerobic uses oxygen, anaerobic does not; aerobic produces carbon dioxide and water, anaerobic produces lactic acid; aerobic transfers much more energy per glucose; aerobic takes place mainly in mitochondria while anaerobic takes place in the cytoplasm; anaerobic involves incomplete oxidation of glucose
2. A student takes 15 breaths per minute with a volume of 0.5 dm3 per breath. During exercise this rises to 30 breaths per minute and 2.0 dm3 per breath. Calculate the increase in volume of air breathed per minute. (3 marks)
Show the mark scheme answer
At rest 15 x 0.5 = 7.5 dm3 per minute; exercise 30 x 2.0 = 60 dm3 per minute; increase = 52.5 dm3 per minute
3. Explain why a person continues to breathe deeply after exercise has finished. (3 marks)
Show the mark scheme answer
Lactic acid built up from anaerobic respiration; this creates an oxygen debt; extra oxygen is needed to react with lactic acid and remove it (Higher tier only)
4.4.2 Respiration FAQs
What does AQA GCSE Biology 4.4.2 Respiration cover?
It covers aerobic and anaerobic respiration, fermentation in yeast, the body's response to exercise, oxygen debt (Higher tier only) and metabolism.
Which paper is 4.4.2 Respiration examined on?
Bioenergetics, including respiration, is assessed on Paper 1.
What equations do I need for respiration?
Learn the word and symbol equations for aerobic respiration, the word equation for anaerobic respiration in muscles (glucose to lactic acid) and the word equation for anaerobic respiration in plants and yeast (glucose to ethanol and carbon dioxide).
